Heretofore, the term "night vision" has been associated with telescope type devices which, by use of an image intensifier, take the small amount of light which exists at night and produces from it an image which can be viewed by the eye or recorded on film.
An early form of night vision device is disclosed by U.S. Pat. No. 1,936,514, granted Nov. 21, 1933, to Thomas C. Lengnick. This patent discloses using an infrared converter with a search light. The infrared image tube converts an infrared image of an object, normally invisible to the human eye, into an image on a glass screen. This infrared converter was the predecessor of modern day image intensifiers.
A state-of-the-art image intensifier is quite well described in U.S. Pat. No. 4,417,814, granted Nov. 29, 1983, to Darrel Doliber. This patent discloses combining with an image intensifier a device for sending an aiming dot out to the object being viewed. Light produced by a light emitting diode (LED) is sharply focused through either an optical fiber or an aperture, measuring somewhere between 0.0003 to 0.010 inch in diameter. The light beam that is produced is seen by the viewer in the form of a small, bright, high color contrast, red aiming point against a yellow-green image of the viewed scene. Devices of this type, involving an aiming dot producing projector in combination with a light intensifier type night viewer, are available from a number of different sources.
U.S. Pat. No. 3,752,983, granted Aug. 14, 1973, to Serge J. Yanez discloses combining together an infrared light source, an image intensifer and a camera. The light source comprises a thirty watt electrical light bulb mounted within a reflector and an infrared filter positioned forwardly of the light bulb and reflector.
Other systems which are known at least in the patent literature, and which should be considered together with the above discussed known devices, for the purpose of putting the subject invention into proper perspective relative to the prior art, are disclosed by the following U.S. patents: U.S. Pat. Nos. 1,969,852, granted Aug. 14, 1934, to Frank J. Markosek; 3,509,344, granted Apr. 28, 1970, to Albert Bouwers; 3,781,560, granted Dec. 25, 1973, to Raymond J. DeBurgh and Harold L. Novick; 3,787,693, granted Jan. 22, 1974, to Robert L. Stone; 3,833,805, granted Sept. 3, 1974, to Charles S. Naiman, E. P. Chicklis and Arthur Linz; 3,989,947, granted Nov. 2, 1976, to Arthur S. Chapman; 4,040,744, granted Aug. 9, 1977, to Charles W. Schertz and Edward H. Ritter; 4,112,300, granted Sept. 5, 1978, to Freeman F. Hall and Jerome J. Redmann; 4,226,529, granted Oct. 7, 1980, to Herbert A. French; 4,290,043, granted Sept. 15, 1981, to Irwin M. Kaplan; 4,315,150, granted Feb. 9, 1982, to Richard F. Darringer, Wayne L. Scharf and James S. Haggerty and 4,376,889, granted Mar. 15, 1983, to David W. Swift.
There is a need for a projector that is capable of projecting, for a considerable distance, a substantial amount of light energy which is invisible to the eye, for illuminating a person or object under surveillance in the dark, for the purpose of brightening the yellow-green image seen by use of an image intensifier up to where a face can be identified and a license plate, or the like, can be read. It is also necessary that the light projector be small in size, be durable in construction, and be relatively inexpensive to manufacture. It is the principal object of the present invention to provide a night light projector which meets this criteria.